This invention relates to a method and an apparatus for detecting the shapes of weld beads.
A welding operation is generally performed at operation sites where atmosphere is liable to be polluted by gases and heated by heat generated in large quantities during the operation and is therefore injurious to human health. Welding operators are thus forced to do their jobs in a considerably poor working environment. In view of this fact, it has hitherto been earnestly desired that automation of a welding operation be realized and manual attention be eliminated.
What is required first of all in effecting automation of a welding operation is to automate detection of the shapes of weld beads, which detection has hitherto been carried out by relying on the human eye. Various apparatus and methods have been proposed and developed for carrying out detection of the shapes of weld beads, etc. However, none of these apparatus and methods have been developed to an extent such that they can have application with success in welding operations of various types in actual practice.
In one detecting apparatus known in the art, a detector capable of detecting a portion of a groove, such as the center or the edges of the groove, is incorporated into a welding machine in a manner such that the detector acts as a unit integral with a welding torch. Such detector carries out detection as it follows the welding torch which is moved over the center or the edges of the groove at all times during the welding operation. When such apparatus is used, it is impossible to detect a change in the width of a groove line where there is a change in the width in some portion thereof and to detect a weld bead, although it is possible to move the welding torch along a groove line. Such detecting apparatus is not capable of enabling an effective welding operation to be performed by accommodating the local change in the width of the groove or in conformity with the weld bead in joining components by welding.
In another method of the prior art for detecting the shapes of weld beads a plurality of detecting elements capable of detecting a vertical displacement from a weld line are arranged perpendicular to the weld line and located equidistantly from one another, and the shapes of the the weld bead are detected on the basis of the amount of displacement detected by such detecting elements. This method has, however, a disadvantage in that the accuracy and precision with which detection is performed may vary depending on the spacing between the detecting elements with a result that it is impossible to perform detection with a high degree of accuracy and precision.
Still another method aiming at improving the aforesaid methods and apparatus of the prior art consists in moving a detecting rod within a groove and determining the central position of the groove and the amplitude of the rod on the basis of the positions of opposite ends of the rod which are brought into contact with the groove face. This method has the disadvantage of being unable to detect the included angle of a groove, the amount of dislocation and the shape of a weld bead.
In automating a welding operation to permit welding of components to be performed automatically without requiring manual attention, it is essential to detect the shape of a weld bead which changes from moment to moment during a welding operation, as well as to detect the positions and dimensions of various parts of the groove, such as the center and the edges thereof, the amount of dislocation and the included angle of the groove. In particular, when multi-layer padding welding is performed, the target position of the welding torch must be varied depending on the shape of a weld bead. Thus, detection of the shape of weld beads is an important factor in producing a sound weld.
The detecting methods of the prior art which have been developed up to the present time are unable to detect the shapes of weld beads or able to detect them only with a low degree of accuracy and precision. Thus, it has hitherto been necessary to provide an operator who keeps watch on the welding operation being performed, even if the welding operation is automated.